An angel of Hashem found her by a spring of water in the wilderness, the spring on the road to Shur.
Classic midrash (angel finds Hagar by the spring)
English: An angel of Hashem found her — teaching that the Holy One prepares the remedy before the blow, and that angels attend to the distress of the compassionate (and of those who suffer).
Supplementary classical material not listed by Torah Temimah under this exact passuk.